Canon 550D vs Pentax 645D

The Canon EOS 550D (called Canon T2i in some regions) and the Pentax 645D are two digital cameras that were revealed to the public, respectively, in February 2010 and March 2010. Both are DSLR (Digital Single Lens Reflex) cameras that are based on an APS-C (550D) and a medium format (645D) sensor. The Canon has a resolution of 17.9 megapixels, whereas the Pentax provides 39.5 MP.

Below is an overview of the main specs of the two cameras as a starting point for the comparison.

Headline Specifications

Canon 550D		Pentax 645D
Digital single lens reflex		Digital single lens reflex
Canon EF mount lenses		Pentax 645 mount lenses
17.9 MP – APS-C sensor		39.5 MP – Medium Format sensor
1080/30p Video		no Video
ISO 100-6,400 (100 - 12,800)		ISO 100-1,600
Optical viewfinder		Optical viewfinder
3.0" LCD – 1040k dots		3.0" LCD – 921k dots
Fixed screen (not touch-sensitive)		Fixed screen (not touch-sensitive)
3.7 shutter flaps per second		1.1 shutter flaps per second
not weather sealed		Weathersealed body
440 shots per battery charge		800 shots per battery charge
129 x 98 x 62 mm, 530 g		156 x 117 x 119 mm, 1480 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Canon EOS 550D and the Pentax 645D? Which one should you buy? Read on to find out how these two cameras compare with respect to their body size, their imaging sensors, their shooting features, their input-output connections, and their reception by expert reviewers.

Body comparison

The physical size and weight of the Canon 550D and the Pentax 645D are illustrated in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive perspectives from the front, the top, and the back are available. All width, height and depth dimensions are rounded to the nearest millimeter.

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Pentax 645D is considerably larger (44 percent) than the Canon 550D. Moreover, the 645D is substantially heavier (179 percent) than the 550D. It is noteworthy in this context that the 645D is splash and dust-proof, while the 550D does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete since they do not consider the interchangeable lenses that both of these cameras require. Hence, you might want to study and compare the specifications of available lenses in order to get the full picture of the size and weight of the two camera systems.

Concerning battery life, the 550D gets 440 shots out of its Canon LP-E8 battery, while the 645D can take 800 images on a single charge of its Pentax D-LI90 power pack.

The following table provides a synthesis of the main physical specifications of the two cameras and other similar ones. In case you want to display and compare another camera duo, you can use the CAM-parator app to select your camera combination among a large number of options.

Body Specifications

		Camera Model	Camera Width	Camera Height	Camera Depth	Camera Weight	Battery Life	Weather Sealing	Camera Launch	Launch Price (USD)	Street Price
1.		Canon 550D	129 mm	98 mm	62 mm	530 g	440	n	Feb 2010	699	ebay.com
2.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
3.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	4,999	ebay.com
4.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	6,799	ebay.com
5.		Canon 500D	129 mm	98 mm	62 mm	520 g	400	n	Mar 2009	799	ebay.com
6.		Canon 600D	133 mm	100 mm	80 mm	570 g	440	n	Feb 2011	599	ebay.com
7.		Canon 650D	133 mm	100 mm	79 mm	575 g	440	n	Jun 2012	849	ebay.com
8.		Canon 700D	133 mm	100 mm	79 mm	580 g	440	n	Mar 2013	649	ebay.com
9.		Canon 750D	132 mm	101 mm	78 mm	555 g	440	n	Feb 2015	749	ebay.com
10.		Canon 760D	132 mm	101 mm	78 mm	565 g	440	n	Feb 2015	649	ebay.com
11.		Canon 1100D	130 mm	100 mm	78 mm	495 g	700	n	Feb 2011	449	ebay.com
12.		Canon 1200D	130 mm	100 mm	78 mm	480 g	500	n	Feb 2014	449	ebay.com
13.		Canon 4000D	129 mm	102 mm	77 mm	436 g	500	n	Feb 2018	399	amazon.com
14.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	21,950	ebay.com
15.		Nikon D3S	160 mm	157 mm	88 mm	1240 g	4200	Y	Oct 2009	5,199	ebay.com
16.		Nikon D5100	128 mm	97 mm	79 mm	560 g	660	n	Apr 2011	749	ebay.com
17.		Pentax 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	8,499	ebay.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Imperial

The price is, of course, an important factor in any camera decision. The manufacturer’s suggested retail prices give an idea on the placement of the camera in the maker’s lineup and the broader market. The 550D was launched at a markedly lower price (by 93 percent) than the 645D, which puts it into a different market segment. Usually, retail prices stay at first close to the launch price, but after several months, discounts become available. Later in the product cycle and, in particular, when the replacement model is about to appear, further discounting and stock clearance sales often push the camera price considerably down. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

Sensor comparison

The size of the imaging sensor is a crucial determinant of image quality. A large sensor will generally have larger individual pixels that offer better low-light sensitivity, provide wider dynamic range, and have richer color-depth than smaller pixels in a sensor of the same technological generation. Furthermore, a large sensor camera will give the photographer more possibilities to use shallow depth-of-field in order to isolate a subject from the background. On the downside, larger sensors tend to be associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Canon 550D features an APS-C sensor and the Pentax 645D a medium format sensor. The sensor area in the 645D is 337 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.6 and 0.79. The sensor in the 550D has a native 3:2 aspect ratio, while the one in the 645D offers a 4:3 aspect.

With 39.5MP, the 645D offers a higher resolution than the 550D (17.9MP), but the 645D nevertheless has larger individual pixels (pixel pitch of 6.06μm versus 4.31μm for the 550D) due to its larger sensor. It is noteworthy in this context that the two cameras were released in close succession, so that their sensors are from the same technological generation. Coming back to sensor resolution, it should be mentioned that the 645D has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

The resolution advantage of the Pentax 645D implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the 645D for good quality output (200 dots per inch) amounts to 36.3 x 27.2 inches or 92.3 x 69.1 cm, for very good quality (250 dpi) 29.1 x 21.8 inches or 73.8 x 55.3 cm, and for excellent quality (300 dpi) 24.2 x 18.1 inches or 61.5 x 46.1 cm. The corresponding values for the Canon 550D are 25.9 x 17.3 inches or 65.8 x 43.9 cm for good quality, 20.7 x 13.8 inches or 52.7 x 35.1 cm for very good quality, and 17.3 x 11.5 inches or 43.9 x 29.3 cm for excellent quality prints.

The Canon EOS 550D has a native sensitivity range from ISO 100 to ISO 6400, which can be extended to ISO 100-12800. The corresponding ISO settings for the Pentax 645D are ISO 100 to ISO 1600 (no boost).

In terms of underlying technology, the 550D is build around a CMOS sensor, while the 645D uses a CCD imager. Both cameras use a Bayer filter for capturing RGB colors on a square grid of photosensors. This arrangement is found in most digital cameras.

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. This service is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). Of the two cameras under consideration, the 645D offers substantially better image quality than the 550D (overall score 16 points higher). The advantage is based on 2.5 bits higher color depth, 1.1 EV in additional dynamic range, and 0.7 stops in additional low light sensitivity. The table below summarizes the physical sensor characteristics and sensor quality findings and compares them across a set of similar cameras.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Canon 550D	APS-C	17.9	5184	3456	1080/30p	22.1	11.5	784	66
2.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
3.		Canon 1D Mark IV	APS-H	16.0	4896	3264	1080/30p	22.8	12.0	1320	74
4.		Canon 1D X	Full Frame	17.9	5184	3456	1080/30p	23.8	11.8	2786	82
5.		Canon 500D	APS-C	15.1	4752	3168	1080/20p	21.7	11.5	663	63
6.		Canon 600D	APS-C	17.9	5184	3456	1080/30p	22.1	11.5	793	65
7.		Canon 650D	APS-C	17.9	5184	3456	1080/30p	21.7	11.2	722	62
8.		Canon 700D	APS-C	17.9	5184	3456	1080/30p	21.7	11.2	681	61
9.		Canon 750D	APS-C	24.0	6000	4000	1080/30p	22.7	12.0	919	71
10.		Canon 760D	APS-C	24.0	6000	4000	1080/30p	22.6	12.0	915	70
11.		Canon 1100D	APS-C	12.2	4272	2848	720/30p	21.9	11.0	755	62
12.		Canon 1200D	APS-C	17.9	5184	3456	1080/30p	21.9	11.3	724	63
13.		Canon 4000D	APS-C	17.9	5184	3456	1080/30p	21.9	11.4	695	63
14.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
15.		Nikon D3S	Full Frame	12.1	4256	2832	720/24p	23.5	12.0	3253	82
16.		Nikon D5100	APS-C	16.1	4928	3264	1080/30p	23.5	13.6	1183	80
17.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101

Many modern cameras are not only capable of taking still images, but also of capturing video footage. The 550D indeed provides movie recording capabilities, while the 645D does not. The highest resolution format that the 550D can use is 1080/30p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. The 550D and the 645D are similar in the sense that both have an optical viewfinder. The latter is useful for getting a clear image for framing even in brightly lit environments. The viewfinder in the 645D offers a wider field of view (98%) than the one in the 550D (95%), so that a larger proportion of the captured image is visible in the finder. In addition, the viewfinder of the 645D has a higher magnification (0.78x vs 0.54x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The following table reports on some other key feature differences and similarities of the Canon 550D, the Pentax 645D, and comparable cameras.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Specifications (inch/000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Max Shutter Speed *	Max Shutter Flaps *	Built-in Flash (yes/no)	Built-in Image Stab
1.		Canon 550D	optical	n	3.0 / 1040	fixed	n	1/4000s	3.7/s	Y	n
2.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
3.		Canon 1D Mark IV	optical	Y	3.0 / 920	fixed	n	1/8000s	10.0/s	n	n
4.		Canon 1D X	optical	Y	3.2 / 1040	fixed	n	1/8000s	14.0/s	n	n
5.		Canon 500D	optical	n	3.0 / 920	fixed	n	1/4000s	3.4/s	Y	n
6.		Canon 600D	optical	n	3.0 / 1040	swivel	n	1/4000s	3.7/s	Y	n
7.		Canon 650D	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
8.		Canon 700D	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
9.		Canon 750D	optical	n	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
10.		Canon 760D	optical	Y	3.0 / 1040	swivel	Y	1/4000s	5.0/s	Y	n
11.		Canon 1100D	optical	n	2.7 / 230	fixed	n	1/4000s	3.0/s	Y	n
12.		Canon 1200D	optical	n	3.0 / 460	fixed	n	1/4000s	3.0/s	Y	n
13.		Canon 4000D	optical	n	2.7 / 230	fixed	n	1/4000s	3.0/s	Y	n
14.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	n
15.		Nikon D3S	optical	Y	3.0 / 921	fixed	n	1/8000s	11.0/s	n	n
16.		Nikon D5100	optical	n	3.0 / 921	swivel	n	1/4000s	4.0/s	Y	n
17.		Pentax 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One difference between the cameras concerns the presence of an on-board flash. The 550D has one, while the 645D does not. While the built-in flash of the 550D is not very powerful, it can at times be useful as a fill-in light.

The Pentax 645D has an intervalometer built-in. This enables the photographer to capture time lapse sequences, such as flower blooming, a sunset or moon rise, without purchasing an external camera trigger and related software.

Concerning the storage of imaging data, both the 550D and the 645D write their files to SDXC cards. The 645D features dual card slots, which can be very useful in case a memory card fails. In contrast, the 550D only has one slot.

Connectivity comparison

For some imaging applications, the extent to which a camera can communicate with its environment can be an important aspect in the camera decision process. The table below provides an overview of the connectivity of the Canon EOS 550D and Pentax 645D and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.

Input-Output Connections

		Camera Model	Hotshoe Port	Internal Mic / Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Canon 550D	Y	stereo / -	Y	-	mini	2.0	-	-	-
2.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
3.		Canon 1D Mark IV	Y	stereo / -	Y	-	mini	2.0	-	-	-
4.		Canon 1D X	Y	mono / -	Y	-	mini	2.0	-	-	-
5.		Canon 500D	Y	mono / mono	-	-	mini	2.0	-	-	-
6.		Canon 600D	Y	mono / mono	Y	-	mini	2.0	-	-	-
7.		Canon 650D	Y	stereo / mono	Y	-	mini	2.0	-	-	-
8.		Canon 700D	Y	stereo / mono	Y	-	mini	2.0	-	-	-
9.		Canon 750D	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
10.		Canon 760D	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
11.		Canon 1100D	Y	stereo / mono	-	-	mini	2.0	-	-	-
12.		Canon 1200D	Y	mono / mono	-	-	mini	2.0	-	-	-
13.		Canon 4000D	Y	mono / mono	-	-	mini	2.0	Y	Y	-
14.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
15.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
16.		Nikon D5100	Y	mono / mono	Y	-	mini	2.0	-	-	-
17.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-

Studio photographers will appreciate that the Pentax 645D (unlike the 550D) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the 550D and the 645D have been discontinued, but can regularly be found used on ebay. The 550D was replaced by the Canon 600D, while the 645D was followed by the Pentax 645Z. Further information on the features and operation of the 550D and 645D can be found, respectively, in the Canon 550D Manual (free pdf) or the online Pentax 645D Manual.

Review summary

So how do things add up? Which of the two cameras – the Canon 550D or the Pentax 645D – has the upper hand? Is one clearly better than the other? A synthesis of the relative strong points of each of the models is listed below.

Arguments in favor of the Canon EOS 550D:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• Broader imaging potential: Can record not only still images but also 1080/30p movies.
• More detailed LCD: Has a higher resolution rear screen (1040k vs 921k dots).
• Faster burst: Shoots at higher frequency (3.7 vs 1.1 flaps/sec) to capture the decisive moment.
• More compact: Is smaller (129x98mm vs 156x117mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 950g or 64 percent) and hence easier to carry around.
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• More affordable: Was introduced into a lower priced category (93 percent cheaper at launch).

Reasons to prefer the Pentax 645D:

• More detail: Has more megapixels (39.5 vs 17.9MP), which boosts linear resolution by 46%.
• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• Better image quality: Scores substantially higher (16 points) in the DXO overall evaluation.
• Richer colors: Generates noticeably more natural colors (2.5 bits more color depth).
• More dynamic range: Captures a broader range of light and dark details (1.1 EV of extra DR).
• Better low-light sensitivity: Can shoot in dim conditions (0.7 stops ISO advantage).
• More complete view: Has a viewfinder with a larger field of view (98% vs 95%).
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.78x vs 0.54x).
• Easier setting verification: Features a control panel on top to check shooting parameters.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Gets more shots (800 versus 440) out of a single battery charge.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.

If the count of individual advantages (bullet points above) is taken as a guide, the 645D is the clear winner of the contest (14 : 8 points). However, the pertinence of the various camera strengths will differ across photographers, so that you might want to weigh individual camera traits according to their importance for your own imaging needs before making a camera decision. A professional wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro shooter. Hence, the decision which camera is best and worth buying is often a very personal one.

How about other alternatives? Do the specifications of the Canon 550D and the Pentax 645D place the cameras among the top in their class? Find out in the latest Best DSLR Camera listing whether the two cameras rank among the cream of the crop.

In any case, while the specs-based evaluation of cameras can be instructive in revealing their potential as photographic tools, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the 550D or the 645D. At times, user reviews, such as those published at amazon, address these issues in a useful manner, but such feedback is on many occasions incomplete, inconsistent, and unreliable.

Expert reviews

This is where reviews by experts come in. The adjacent summary-table relays the overall verdicts of several of the most popular camera review sites (amateurphotographer [AP], cameralabs [CL], digitalcameraworld [DCW], dpreview [DPR], ephotozine [EPZ], photographyblog [PB]). As can be seen, the professional reviewers agree in many cases on the quality of different cameras, but sometimes their assessments diverge, reinforcing the earlier point that a camera decision is often a very personal choice.

Expert Camera Reviews

		Camera   Model	AP   score	CL   score	DCW   score	DPR   score	EPZ   score	PB   score	Camera Launch	Launch Price (USD)	Street Price
1.		Canon 550D	..	+ +	..	77/100	4/5	4.5/5	Feb 2010	699	ebay.com
2.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
3.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	4,999	ebay.com
4.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	6,799	ebay.com
5.		Canon 500D	..	+ +	..	74/100	4.5/5	4.5/5	Mar 2009	799	ebay.com
6.		Canon 600D	3/5	o	..	77/100	4.5/5	4.5/5	Feb 2011	599	ebay.com
7.		Canon 650D	4/5	+ +	..	77/100	4.5/5	4.5/5	Jun 2012	849	ebay.com
8.		Canon 700D	..	..	..	76/100	4.5/5	4.5/5	Mar 2013	649	ebay.com
9.		Canon 750D	5/5	..	..	75/100	4.5/5	4.5/5	Feb 2015	749	ebay.com
10.		Canon 760D	5/5	+	..	77/100	4.5/5	4.5/5	Feb 2015	649	ebay.com
11.		Canon 1100D	..	80/100	..	69/100	4/5	4.5/5	Feb 2011	449	ebay.com
12.		Canon 1200D	3/5	+	..	..	4/5	4.5/5	Feb 2014	449	ebay.com
13.		Canon 4000D	2.5/5	o	3/5	..	3.5/5	3.5/5	Feb 2018	399	amazon.com
14.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	21,950	ebay.com
15.		Nikon D3S	5/5	..	..	89/100	4.5/5	5/5	Oct 2009	5,199	ebay.com
16.		Nikon D5100	5/5	+ +	..	76/100	4.5/5	4.5/5	Apr 2011	749	ebay.com
17.		Pentax 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	8,499	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, though. The ratings were established in reference to similarly priced cameras that were available in the market at the time of the review. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. Also, please note that some of the review sites have changed their methodology and reporting over time.

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Other camera comparisons

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